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  • Java graphic objects as in flashgames

    - by Ryu Kajiya
    How is it possible (with the standard Java2D engine) to use small sprites like graphic objects? For those who don't know what I mean, in all those Flash-games like on Facebook they put small sprites on the screen which react to mouse-over and clicks. I tried to do the same in Java but can't find a good method. Swing components always spread over the whole bitmap, but I only want to get a reaction from the object when the mouse is over a pixel that's not transparent. So basically checking every time if the object below the mouse contains a non-transparent pixel (which i believe could be pretty intense in a gameloop or repaint loop). I have no idea how to implement such a thing efficiently.

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  • How should I define my Java Objects?

    - by HonorGod
    I have a data grid where I sort of show the following information - All Guests Total Adults = 22 Total Children = 27 Confirmed Total Adults = 9 Total Children = 13 Country = Germany Total Adults = 5 Total Childres = 6 Friends Adults = 2 Children = 2 Relatives Adults = 3 Children = 4 Country = USA Total Adults = 4 Total Childres = 7 Friends Adults = 2 Children = 5 Relatives Adults = 2 Children = 2 Tentative Total Adults = 13 Total Children - 14 Country = Australia Total Adults = 7 Total Childres = 8 Friends Adults = 2 Children = 3 Relatives Adults = 5 Children = 5 Country = China Total Adults = 6 Total Childres = 6 Friends Adults = 2 Children = 4 Relatives Adults = 4 Children = 2 And in the database what I have is data at the lowest level which is Friends / Relatives and the corresponding countries set as a look-up value which in indirectly connected to another look-up that can tell me if they fall under confirmed or tentative. I guess my question is how do I layout my Java Object and perform the aggregations and give it back to the client. I am not sure if I am clear with my question, but feel free to comment so I can update the question accordingly.

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  • spliiting code in java-don't know what's wrong [closed]

    - by ???? ?????
    I'm writing a code to split a file into many files with a size specified in the code, and then it will join these parts later. The problem is with the joining code, it doesn't work and I can't figure what is wrong! This is my code: import java.io.*; import java.util.*; public class StupidSplit { static final int Chunk_Size = 10; static int size =0; public static void main(String[] args) throws IOException { String file = "b.txt"; int chunks = DivideFile(file); System.out.print((new File(file)).delete()); System.out.print(JoinFile(file, chunks)); } static boolean JoinFile(String fname, int nChunks) { /* * Joins the chunks together. Chunks have been divided using DivideFile * function so the last part of filename will ".partxxxx" Checks if all * parts are together by matching number of chunks found against * "nChunks", then joins the file otherwise throws an error. */ boolean successful = false; File currentDirectory = new File(System.getProperty("user.dir")); // File[] fileList = currentDirectory.listFiles(); /* populate only the files having extension like "partxxxx" */ List<File> lst = new ArrayList<File>(); // Arrays.sort(fileList); for (File file : fileList) { if (file.isFile()) { String fnm = file.getName(); int lastDot = fnm.lastIndexOf('.'); // add to list which match the name given by "fname" and have //"partxxxx" as extension" if (fnm.substring(0, lastDot).equalsIgnoreCase(fname) && (fnm.substring(lastDot + 1)).substring(0, 4).equals("part")) { lst.add(file); } } } /* * sort the list - it will be sorted by extension only because we have * ensured that list only contains those files that have "fname" and * "part" */ File[] files = (File[]) lst.toArray(new File[0]); Arrays.sort(files); System.out.println("size ="+files.length); System.out.println("hello"); /* Ensure that number of chunks match the length of array */ if (files.length == nChunks-1) { File ofile = new File(fname); FileOutputStream fos; FileInputStream fis; byte[] fileBytes; int bytesRead = 0; try { fos = new FileOutputStream(ofile,true); for (File file : files) { fis = new FileInputStream(file); fileBytes = new byte[(int) file.length()]; bytesRead = fis.read(fileBytes, 0, (int) file.length()); assert(bytesRead == fileBytes.length); assert(bytesRead == (int) file.length()); fos.write(fileBytes); fos.flush(); fileBytes = null; fis.close(); fis = null; } fos.close(); fos = null; } catch (FileNotFoundException fnfe) { System.out.println("Could not find file"); successful = false; return successful; } catch (IOException ioe) { System.out.println("Cannot write to disk"); successful = false; return successful; } /* ensure size of file matches the size given by server */ successful = (ofile.length() == StupidSplit.size) ? true : false; } else { successful = false; } return successful; } static int DivideFile(String fname) { File ifile = new File(fname); FileInputStream fis; String newName; FileOutputStream chunk; //int fileSize = (int) ifile.length(); double fileSize = (double) ifile.length(); //int nChunks = 0, read = 0, readLength = Chunk_Size; int nChunks = 0, read = 0, readLength = Chunk_Size; byte[] byteChunk; try { fis = new FileInputStream(ifile); StupidSplit.size = (int)ifile.length(); while (fileSize > 0) { if (fileSize <= Chunk_Size) { readLength = (int) fileSize; } byteChunk = new byte[readLength]; read = fis.read(byteChunk, 0, readLength); fileSize -= read; assert(read==byteChunk.length); nChunks++; //newName = fname + ".part" + Integer.toString(nChunks - 1); newName = String.format("%s.part%09d", fname, nChunks - 1); chunk = new FileOutputStream(new File(newName)); chunk.write(byteChunk); chunk.flush(); chunk.close(); byteChunk = null; chunk = null; } fis.close(); System.out.println(nChunks); // fis = null; } catch (FileNotFoundException fnfe) { System.out.println("Could not find the given file"); System.exit(-1); } catch (IOException ioe) { System.out .println("Error while creating file chunks. Exiting program"); System.exit(-1); }System.out.println(nChunks); return nChunks; } } }

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  • Facing Problems While Installing Java

    - by user100381
    First When i downloaded java from official website i got confused how to install it. den i searched it on software center and i got it. but wen i install it, it starts but instantly stops and the line highlighting the installation status in progress tab doesn't move forward.den i searched on internet and tried installing it by terminal but he terminal says that u have to first configure something that i dont know but it tells me to run this command-"sudo dpkg-configure -a" and when i run this command the terminal process stops in the middle and even after leaving it for about an hour it doesn't proceed further.. after that when i press the close button of the terminal if shows that some tasks are in progress and closing the terminal would...bla bla bla... so i am greatly confused because even other software's like gimp image editor and all are not getting installed.. please help me..!!

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  • Java Extends value not updating

    - by James116
    I am currently working on a hibernate project(EJB and JSF), and i have multiple java classes. The data of parent is being change in the front end with JSF, however, it is not updating in the child class. Any idea as to what could be causing this? This is what i was doing. public class parent{ private String x = "UNKNOWN"; //Getters and setters public getX(){ } } public class child extends parent{ public string y{ //this is return UNKNOWN //instead of the new value being change by the user System.out.print(getX()); } } Thanks in advance

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  • Game Database Connectivity Java

    - by The Kraken
    I'm developing a simple multi-player puzzle game in Java. Both players should be able to view the same game board on his own computer. Then, when one player makes an action in the game (ex. drags an object onto a coordinate space), the game's view should update automatically on the other computer's game screen. I'd like all this to happen over the internet, not requiring both computers to be on the same LAN connection. If I need to use SQL/PHP to accomplish this, I'm unsure how to design the database to accomplish something as simple as the following: Player A drags element onscreen Game sends coordinates of element to database/server Player B's computer detects a change to an item in the database Player B's computer grabs the coordinates of Player A's item Player B's machine draws onscreen elements at the received coordinates Could somebody point me in the right direction?

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  • How to solve this nullPointer Exception in jasper report?

    - by Kumar
    Hi, I am new to jasper report, I need to create pdf document with BeanDatasource and subreport. I refer the following blog " http://knol.google.com/k/jasper-reports-working-with-beans-and-sub-report# " . I followed all the steps perfectly. While i am running the report using IReport i can get the pdf document with the content. But when we try to create from java program i m getting exception in the following line Line number 110: " JasperFillManager.fillReportToFile("C:/JasperReports/contacts.jasper", parameters, new JRBeanCollectionDataSource(TestPerson.getBeanCollection())); " and this is the following error i am getting in my Eclipse Console window . java.lang.NullPointerException at net.sf.jasperreports.engine.JRPropertiesMap.readObject(JRPropertiesMap.java:185) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at java.io.ObjectStreamClass.invokeReadObject(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readArray(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readObject(Unknown Source) at net.sf.jasperreports.engine.util.JRLoader.loadObject(JRLoader.java:88) at net.sf.jasperreports.engine.util.JRLoader.loadObjectFromLocation(JRLoader.java:257) at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateSubreport(JRFillSubreport.java:308) at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluate(JRFillSubreport.java:257) at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:275) at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:426) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:1380) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:692) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:255) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:113) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:891) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:814) at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:89) at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:601) at test.TestJasperReport.main(TestJasperReport.java:110)

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  • Java update/install via group policy

    - by Maximus
    I trying to deploy the latest Java RE version via GP, Java 7 update 9. I want to update computers that are currently running an older version of Java, a mixture of 7.6 and 7.7, some computers are running versions as old as 6.31. Some are running a mixture of both. I would also like this GP to install Java if it's not installed. Previously I used push out Java updates to users machines as Java didn't remove the old version. So when it was done the user would restart their browser or pc to start using the latest version. Not the best way to manage it as it leaves the old version installed but it worked. I've created group policies before for printer deployment, log on drive mapping scripts, but never software deployment. I've extracted the Java MSI and created a transform file to suppress reboot etc using orca. As described on this site http://ivan.dretvic.com/2011/06/how-to-package-and-deploy-java-jre-1-6-0_26-via-group-policy/. I have also tried saving the edited MSI directly and that didn't work either. But it just won't deploy. I have tried to enable logging as suggested on this site http://openofficetechnology.com/node/32, GPO logging via UserEnvDebugLevel, Software deployment logging via AppmgmtDebugLevel and MSI logging, but there is no log C:\Windows\Debug\UserMode\userenv.log being created. The windows event viewer has the following errors: Error 24/10/2012 11:44:04 AM - "Failed to apply changes to software installation settings. Software changes could not be applied. A previous log entry with details should exist. The error was : %%1612" Information 24/10/2012 11:44:04 AM - "The removal of the assignment of application Java 7 Update 9 - FB Java Transform from policy JavaDeploy succeeded." Error 24/10/2012 11:44:04 AM - "The install of application Java 7 Update 9 - FB Java Transform from policy JavaDeploy failed. The error was : %%1612" There is a log created for MSI logging and it's as below. It says the source is invalid but it exists on the share and the PC that I'm testing has permissions and I've included the recommendation here Group Policy installation failed error 1274 to enable "Always wait for the network at computer startup and logon" === Verbose logging started: 24/10/2012 11:43:59 Build type: SHIP UNICODE 5.00.7601.00 Calling process: C:\Windows\system32\svchost.exe === MSI (c) (9C:EC) [11:43:59:898]: Resetting cached policy values MSI (c) (9C:EC) [11:43:59:898]: Machine policy value 'Debug' is 3 MSI (c) (9C:EC) [11:43:59:898]: ******* RunEngine: ******* Product: {26a24ae4-039d-4ca4-87b4-2f83217009ff} ******* Action: ******* CommandLine: ********** MSI (c) (9C:EC) [11:43:59:898]: Client-side and UI is none or basic: Running entire install on the server. MSI (c) (9C:EC) [11:43:59:898]: Grabbed execution mutex. MSI (c) (9C:EC) [11:44:03:431]: Cloaking enabled. MSI (c) (9C:EC) [11:44:03:431]: Attempting to enable all disabled privileges before calling Install on Server MSI (c) (9C:EC) [11:44:03:439]: Incrementing counter to disable shutdown. Counter after increment: 0 MSI (s) (2C:70) [11:44:03:574]: Running installation inside multi-package transaction {26a24ae4-039d-4ca4-87b4-2f83217009ff} MSI (s) (2C:70) [11:44:03:574]: Grabbed execution mutex. MSI (s) (2C:7C) [11:44:03:607]: Resetting cached policy values MSI (s) (2C:7C) [11:44:03:607]: Machine policy value 'Debug' is 3 MSI (s) (2C:7C) [11:44:03:607]: ******* RunEngine: ******* Product: {26a24ae4-039d-4ca4-87b4-2f83217009ff} ******* Action: ******* CommandLine: ********** MSI (s) (2C:7C) [11:44:03:607]: Machine policy value 'DisableUserInstalls' is 0 MSI (s) (2C:7C) [11:44:03:623]: User policy value 'SearchOrder' is 'nmu' MSI (s) (2C:7C) [11:44:03:624]: User policy value 'DisableMedia' is 0 MSI (s) (2C:7C) [11:44:03:624]: Machine policy value 'AllowLockdownMedia' is 0 MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Media enabled only if package is safe. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Looking for sourcelist for product {26a24ae4-039d-4ca4-87b4-2f83217009ff} MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Adding {26a24ae4-039d-4ca4-87b4-2f83217009ff}; to potential sourcelist list (pcode;disk;relpath). MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Now checking product {26a24ae4-039d-4ca4-87b4-2f83217009ff} MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Media is enabled for product. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Attempting to use LastUsedSource from source list. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Processing net source list. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Trying source \\server\share\deployment\Java\stable\x32\. MSI (s) (2C:7C) [11:44:03:650]: Note: 1: 2303 2: 5 3: \\server\share\ MSI (s) (2C:7C) [11:44:03:650]: Note: 1: 1325 2: deployment MSI (s) (2C:7C) [11:44:03:650]: ConnectToSource: CreatePath/CreateFilePath failed with: -2147483648 1325 -2147483648 MSI (s) (2C:7C) [11:44:03:650]: ConnectToSource (con't): CreatePath/CreateFilePath failed with: -2147483648 -2147483648 MSI (s) (2C:7C) [11:44:03:650]: SOURCEMGMT: net source '\\server\share\deployment\Java\stable\x32\' is invalid. MSI (s) (2C:7C) [11:44:03:650]: Note: 1: 1706 2: -2147483647 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:03:650]: SOURCEMGMT: Processing media source list. MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 2203 2: 3: -2147287037 MSI (s) (2C:7C) [11:44:04:668]: SOURCEMGMT: Source is invalid due to missing/inaccessible package. MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1706 2: -2147483647 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:04:668]: SOURCEMGMT: Processing URL source list. MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1402 2: UNKNOWN\URL 3: 2 MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1706 2: -2147483647 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1706 2: 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:04:668]: SOURCEMGMT: Failed to resolve source MSI (s) (2C:7C) [11:44:04:668]: MainEngineThread is returning 1612 MSI (s) (2C:70) [11:44:04:670]: User policy value 'DisableRollback' is 0 MSI (s) (2C:70) [11:44:04:670]: Machine policy value 'DisableRollback' is 0 MSI (s) (2C:70) [11:44:04:670]: Incrementing counter to disable shutdown. Counter after increment: 0 MSI (s) (2C:70) [11:44:04:670]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\Rollback\Scripts 3: 2 MSI (s) (2C:70) [11:44:04:671]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\Rollback\Scripts 3: 2 MSI (s) (2C:70) [11:44:04:671]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\InProgress 3: 2 MSI (s) (2C:70) [11:44:04:671]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\InProgress 3: 2 MSI (s) (2C:70) [11:44:04:671]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied. Counter after decrement: -1 MSI (s) (2C:70) [11:44:04:671]: Restoring environment variables MSI (c) (9C:EC) [11:44:04:675]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied. Counter after decrement: -1 MSI (c) (9C:EC) [11:44:04:675]: MainEngineThread is returning 1612 === Verbose logging stopped: 24/10/2012 11:44:04 === I'm not sure what my next approach should be. Any help would be much appreciated. Thanks.

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  • NoSuchPortException using RXTX Java library on Windows?

    - by Steve
    I have followed the instructions to setup rxtx on windows from http://www.jcontrol.org/download/readme_rxtx_en.html. What I did exactly was copy rxtxSerial.dll to "C:\Program Files\Java\jdk1.6.0_07\jre\bin" and copied RXTXcomm.jar to "C:\Program Files\Java\jdk1.6.0_07\jre\lib\ext" (my JAVA_HOME variable is set to C:\Program Files\Java\jdk1.6.0_07\jre) I also added RXTXcomm.jar to my eclipse project. But when I run it, it still says "NoSuchPortException" Devel Library ========================================= Native lib Version = RXTX-2.0-7pre1 Java lib Version = RXTX-2.0-7pre1 java.lang.ClassCastException: gnu.io.RXTXCommDriver cannot be cast to gnu.io.CommDriver thrown while loading gnu.io.RXTXCommDriver gnu.io.NoSuchPortException at gnu.io.CommPortIdentifier.getPortIdentifier(CommPortIdentifier.java:218) at TwoWaySerialComm.connect(TwoWaySerialComm.java:20) at TwoWaySerialComm.main(TwoWaySerialComm.java:107) In my java file, I tell it: try { (new TwoWaySerialComm()).connect("COM4"); } and I've also tried the Java Comm API. Both cannot recognize my serial port but I am sure I followed the instruction correctly. There files are there. Does anybody have any idea what it could be?

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  • bash - how to filter java exception info

    - by Michael Mao
    Hi all: We've got a multi-agent Java environment where different agent would most likely produce all sorts of exceptions thrown to stderr. Here is a sample taken from the huge exception log **java.security.AccessControlException: access denied (java.io.FilePermission ..\tournament\Driver\HotelRoomAnalyser.class read)** at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkRead(Unknown Source) at java.io.File.length(Unknown Source) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClass(EmarketSandbox.java:199) at java.lang.ClassLoader.loadClass(Unknown Source) **java.security.AccessControlException: access denied (java.io.FilePermission ..\tournament\Driver\HotelRoomAnalyser.class read)** at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkRead(Unknown Source) at java.io.File.length(Unknown Source) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClass(EmarketSandbox.java:199) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) at MySmarterAgent.hotelRoomBookings(MySmarterAgent.java:108) fortunately all top-tier exceptions are denoted by no leading spaces, as wrapped by ** above. My concern is to get all of the top-tier exception name (delimited by colon :), together with the first line below which contains something like at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) Basically, something with padded style, starts with "at" and ends with ".java:108" So this info can be forwarded to the owner of that error-prone agent and let him/her fix it. My code in ~/.bashrc is incompleted now : alias startmatch='java -jar "emarket.jar" ../tournament 100'; function geterrors() { startmatch 2>"$1"; a=0; while read line do if true; then a=$(($a+1)); echo $a; fi; done } What it does now is to redirect all stderr to a text file specified by the first argument passed in, and after that, parse that text file line by line, if certain conditions returns true, echo only that line. And I am stuck with what to do inside the loop. Any suggestion is much appreciates, any hint is welcomed.

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  • What is the difference between Java RMI and JMS?

    - by Sanoj
    When designing an distributed application in Java there seams to be a few technologies that address the same kind of problem. I have briefly read about Java Remote Method Invocation and Java Message Service, but it is hard to really see the difference. Java RMI seams to be more tightly coupled than JMS because JMS use asynchronous communication, but otherwise I don't see any big differences. What is the difference between them? Is one of them newer than the other one? Which one is more common/popular in enterprises? What advantages do they have over eachother? When is one preferred over the other? Do they differ much in how difficult they are to implement? I also think that Web Services and CORBA address the same problem.

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  • Is there a java library / package analogous to <stdio.h>?

    - by Roboprog
    I have been doing Java on and off for about 14 years, and almost nothing else the last 6 years or so. I really hate the java.io package -- its legion of subclasses and adapters. I do like exceptions, rather than having to always poll "errno" and the like, but I could surely live without declared exceptions. Is there anything that functions like the Unix/ANSI stdio.h routines in C? I know we will never be rid of java.io and its conventions until java itself is retired, as they have metastasized throughout the many frameworks that have accreted to java. That said, I would like something that works kind of like this (let's call it package javax.stdio): Have a main utility class, perhaps FileStar, that can read and write files (or pipes), either text or binary, either sequentially or random access, with constructors that mimic fopen() and popen(). This class should have a load of useful methods that do things like fread(), fwrite(), fgets(), fputs(), fseek(), and whatever else (fprintf()?). Methods that are incompatible with the open/construct mode simply throw up (just like some of the collections classes/methods do when restricted). Then, have a bunch of interfaces that suggest how you intend to use the stream once you have created it: Sequential, RandomAccess, ReadOnly, WriteOnly, Text, Binary, plus combinations of these that make sense. Perhaps even have methods to return the appropriate type-cast (interface), throwing up if you have asked for something incompatible. For extra flavor, skip the declared exceptions -- e.g. - javax.stdio.IOException extends RuntimeException. Is there an open source project like this floating around?

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  • Problem with relative file path

    - by Richard Knop
    So here is my program, which works ok: import java.io.FileReader; import java.io.BufferedReader; import java.io.IOException; import java.util.Scanner; import java.util.Locale; public class ScanSum { public static void main(String[] args) throws IOException { Scanner s = null; double sum = 0; try { s = new Scanner(new BufferedReader(new FileReader("D:/java-projects/HelloWorld/bin/usnumbers.txt"))); s.useLocale(Locale.US); while (s.hasNext()) { if (s.hasNextDouble()) { sum += s.nextDouble(); } else { s.next(); } } } finally { s.close(); } System.out.println(sum); } } As you can see, I am using absolute path to the file I am reading from: s = new Scanner(new BufferedReader(new FileReader("D:/java-projects/HelloWorld/bin/usnumbers.txt"))); The problem arises when I try to use the relative path: s = new Scanner(new BufferedReader(new FileReader("usnumbers.txt"))); I get an error: Exception in thread "main" java.lang.NullPointerException at ScanSum.main(ScanSum.java:24) The file usnumbers.txt is in the same directory as the ScanSum.class file: D:/java-projects/HelloWorld/bin/ScanSum.class D:/java-projects/HelloWorld/bin/usnumbers.txt How could I solve this?

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  • google calendar api (java) authentication error in dynamic web project

    - by HazProblem
    org.springframework.web.util.NestedServletException: Handler processing failed; nested exception is java.lang.NoClassDefFoundError: com/google/gdata/util/AuthenticationException org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:823) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560) javax.servlet.http.HttpServlet.service(HttpServlet.java:641) javax.servlet.http.HttpServlet.service(HttpServlet.java:722) org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) The class i have written works fine as a normal java application, but when i try to use the code in an dynamic web project i get this authentication failure. Where´s the difference?

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  • class hierarchy design for small java project

    - by user523956
    I have written a java code which does following:- Main goal is to fetch emails from (inbox, spam) folders and store them in database. It fetches emails from gmail,gmx,web.de,yahoo and Hotmail. Following attributes are stored in mysql database. Slno, messagedigest, messageid, foldername, dateandtime, receiver, sender, subject, cc, size and emlfile. For gmail,gmy and web.de, I have used javamail API, because email form it can be fetched with IMAP. For yahoo and hotmail, I have used html parser and httpclient to fetch emails form spam folder and for inbox folder, I have used pop3 javamail API. I want to have proper class hierarchy which makes my code efficient and easily reusable. As of now I have designed class hierarchy as below: I am sure it can still be improved. So I would like to have different opinions on it. I have following classes and methods as of now. MainController:- Here I pass emailid, password and foldername from which emails have to be fetched. Abstract Class :-EmailProtocol Abstract Methods of it (All methods except executeParser contains method definition):- connectImap() // used by gmx,gmail and web.de email ids connectPop3() // used by hotmail and yahoo to fetch emails of inbox folder createMessageDigest // used by every email provider(gmx, gmail,web.de,yahoo,hotmail) establishDBConnection // used by every email emailAlreadyExists // used by every email which checks whether email already exists in db or not, if not then store it. storeemailproperties // used by every email to store emails properties to mysql database executeParser // nothing written in it. Overwridden and used by just hotmail and yahoo to fetch emails form spam folder. Imap extends EmailProtocol (nothing in it. But I have to have it to access methods of EmailProtocol. This is used to fetch emails from gmail,gmx and web.de) I know this is really a bad way but don't know how to do it other way. Hotmsil extends EmailProtocol Methods:- executeParser() :- This is used by just hotmail email id. fetchjunkemails() :- This is also very specific for only hotmail email id. Yahoo extends EmailProtocol Methods:- executeParser() storeEmailtotemptable() MoveEmailtoInbox() getFoldername() nullorEquals() All above methods are specific for yahoo email id. public DateTimeFormat(class) format() //this formats datetime of gmax,gmail and web.de emails. formatYahoodate //this formats datetime of yahoo email. formatHotmaildate // this formats datetime of hotmail email. public StringFormat ConvertStreamToString() // Accessed by every class except DateTimeFormat class. formatFromTo() // Accessed by every class except DateTimeFormat class. public Class CheckDatabaseExistance public static void checkForDatabaseTablesAvailability() (This method checks at the beginnning whether database and required tables exist in mysql or not. if not it creates them) Please see code of my MainController class so that You can have an idea about how I use different classes. public class MainController { public static void main(String[] args) throws Exception { ArrayList<String> web_de_folders = new ArrayList<String>(); web_de_folders.add("INBOX"); web_de_folders.add("Unbekannt"); web_de_folders.add("Spam"); web_de_folders.add("OUTBOX"); web_de_folders.add("SENT"); web_de_folders.add("DRAFTS"); web_de_folders.add("TRASH"); web_de_folders.add("Trash"); ArrayList<String> gmx_folders = new ArrayList<String>(); gmx_folders.add("INBOX"); gmx_folders.add("Archiv"); gmx_folders.add("Entwürfe"); gmx_folders.add("Gelöscht"); gmx_folders.add("Gesendet"); gmx_folders.add("Spamverdacht"); gmx_folders.add("Trash"); ArrayList<String> gmail_folders = new ArrayList<String>(); gmail_folders.add("Inbox"); gmail_folders.add("[Google Mail]/Spam"); gmail_folders.add("[Google Mail]/Trash"); gmail_folders.add("[Google Mail]/Sent Mail"); ArrayList<String> pop3_folders = new ArrayList<String>(); pop3_folders.add("INBOX"); CheckDatabaseExistance.checkForDatabaseTablesAvailability(); EmailProtocol imap = new Imap(); System.out.println("CHECKING FOR NEW EMAILS IN WEB.DE...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", web_de_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN GMX.DE...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", gmx_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN GMAIL...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", gmail_folders); EmailProtocol yahoo = new Yahoo(); Yahoo y=new Yahoo(); System.out.println("\nEXECUTING YAHOO PARSER"); System.out.println("*********************************************************************************"); y.executeParser("http://de.mc1321.mail.yahoo.com/mc/welcome?ymv=0","[email protected]","pwd"); System.out.println("\nCHECKING FOR NEW EMAILS IN INBOX OF YAHOO (POP3)"); System.out.println("*********************************************************************************"); yahoo.connectPop3("[email protected]","pwd",pop3_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN INBOX OF HOTMAIL (POP3)"); System.out.println("*********************************************************************************"); yahoo.connectPop3("[email protected]","pwd",pop3_folders); EmailProtocol hotmail = new Hotmail(); Hotmail h=new Hotmail(); System.out.println("\nEXECUTING HOTMAIL PARSER"); System.out.println("*********************************************************************************"); h.executeParser("https://login.live.com/ppsecure/post.srf","[email protected]","pwd"); } } I have kept DatetimeFormat and StringFormat class public so that I can access its public methods by just (DatetimeFormat.formatYahoodate for e.g. from different methods). This is the first time I have developed something in java. It serves its purpose but of course code is still not so efficient I think. I need your suggestions on this project.

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  • Java collision detection and player movement: tips

    - by Loris
    I have read a short guide for game develompent (java, without external libraries). I'm facing with collision detection and player (and bullets) movements. Now i put the code. Most of it is taken from the guide (should i link this guide?). I'm just trying to expand and complete it. This is the class that take care of updates movements and firing mechanism (and collision detection): public class ArenaController { private Arena arena; /** selected cell for movement */ private float targetX, targetY; /** true if droid is moving */ private boolean moving = false; /** true if droid is shooting to enemy */ private boolean shooting = false; private DroidController droidController; public ArenaController(Arena arena) { this.arena = arena; this.droidController = new DroidController(arena); } public void update(float delta) { Droid droid = arena.getDroid(); //droid movements if (moving) { droidController.moveDroid(delta, targetX, targetY); //check if arrived if (droid.getX() == targetX && droid.getY() == targetY) moving = false; } //firing mechanism if(shooting) { //stop shot if there aren't bullets if(arena.getBullets().isEmpty()) { shooting = false; } for(int i = 0; i < arena.getBullets().size(); i++) { //current bullet Bullet bullet = arena.getBullets().get(i); System.out.println(bullet.getBounds()); //angle calculation double angle = Math.atan2(bullet.getEnemyY() - bullet.getY(), bullet.getEnemyX() - bullet.getX()); //increments x and y bullet.setX((float) (bullet.getX() + (Math.cos(angle) * bullet.getSpeed() * delta))); bullet.setY((float) (bullet.getY() + (Math.sin(angle) * bullet.getSpeed() * delta))); //collision with obstacles for(int j = 0; j < arena.getObstacles().size(); j++) { Obstacle obs = arena.getObstacles().get(j); if(bullet.getBounds().intersects(obs.getBounds())) { System.out.println("Collision detect!"); arena.removeBullet(bullet); } } //collisions with enemies for(int j = 0; j < arena.getEnemies().size(); j++) { Enemy ene = arena.getEnemies().get(j); if(bullet.getBounds().intersects(ene.getBounds())) { System.out.println("Collision detect!"); arena.removeBullet(bullet); } } } } } public boolean onClick(int x, int y) { //click on empty cell if(arena.getGrid()[(int)(y / Arena.TILE)][(int)(x / Arena.TILE)] == null) { //coordinates targetX = x / Arena.TILE; targetY = y / Arena.TILE; //enables movement moving = true; return true; } //click on enemy: fire if(arena.getGrid()[(int)(y / Arena.TILE)][(int)(x / Arena.TILE)] instanceof Enemy) { //coordinates float enemyX = x / Arena.TILE; float enemyY = y / Arena.TILE; //new bullet Bullet bullet = new Bullet(); //start coordinates bullet.setX(arena.getDroid().getX()); bullet.setY(arena.getDroid().getY()); //end coordinates (enemie) bullet.setEnemyX(enemyX); bullet.setEnemyY(enemyY); //adds bullet to arena arena.addBullet(bullet); //enables shooting shooting = true; return true; } return false; } As you can see for collision detection i'm trying to use Rectangle object. Droid example: import java.awt.geom.Rectangle2D; public class Droid { private float x; private float y; private float speed = 20f; private float rotation = 0f; private float damage = 2f; public static final int DIAMETER = 32; private Rectangle2D rectangle; public Droid() { rectangle = new Rectangle2D.Float(x, y, DIAMETER, DIAMETER); } public float getX() { return x; } public void setX(float x) { this.x = x; //rectangle update rectangle.setRect(x, y, DIAMETER, DIAMETER); } public float getY() { return y; } public void setY(float y) { this.y = y; //rectangle update rectangle.setRect(x, y, DIAMETER, DIAMETER); } public float getSpeed() { return speed; } public void setSpeed(float speed) { this.speed = speed; } public float getRotation() { return rotation; } public void setRotation(float rotation) { this.rotation = rotation; } public float getDamage() { return damage; } public void setDamage(float damage) { this.damage = damage; } public Rectangle2D getRectangle() { return rectangle; } } For now, if i start the application and i try to shot to an enemy, is immediately detected a collision and the bullet is removed! Can you help me with this? If the bullet hit an enemy or an obstacle in his way, it must disappear. Ps: i know that the movements of the bullets should be managed in another class. This code is temporary. update I realized what happens, but not why. With those for loops (which checks collisions) the movements of the bullets are instantaneous instead of gradual. In addition to this, if i add the collision detection to the Droid, the method intersects returns true ALWAYS while the droid is moving! public void moveDroid(float delta, float x, float y) { Droid droid = arena.getDroid(); int bearing = 1; if (droid.getX() > x) { bearing = -1; } if (droid.getX() != x) { droid.setX(droid.getX() + bearing * droid.getSpeed() * delta); //obstacles collision detection for(Obstacle obs : arena.getObstacles()) { if(obs.getRectangle().intersects(droid.getRectangle())) { System.out.println("Collision detected"); //ALWAYS HERE } } //controlla se è arrivato if ((droid.getX() < x && bearing == -1) || (droid.getX() > x && bearing == 1)) droid.setX(x); } bearing = 1; if (droid.getY() > y) { bearing = -1; } if (droid.getY() != y) { droid.setY(droid.getY() + bearing * droid.getSpeed() * delta); if ((droid.getY() < y && bearing == -1) || (droid.getY() > y && bearing == 1)) droid.setY(y); } }

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  • JMS MQ Connection closed in JSF 2 SessionBean

    - by veote
    I use Websphere Application Server 8 with MQ Series as Messaging Queue. When I open close the connection in sessionbean in a "postConstruct" method and I use it in another method then its closed. My Code is: import java.io.Serializable; import javax.annotation.PostConstruct; import javax.annotation.PreDestroy; import javax.annotation.Resource; import javax.faces.application.FacesMessage; import javax.faces.bean.ManagedBean; import javax.faces.bean.SessionScoped; import javax.faces.context.FacesContext; import javax.jms.JMSException; import javax.jms.Queue; import javax.jms.QueueConnection; import javax.jms.QueueConnectionFactory; import javax.jms.QueueSender; import javax.jms.QueueSession; import javax.jms.Session; import javax.jms.TextMessage; @ManagedBean @SessionScoped public class MQRequest implements Serializable { private static final long serialVersionUID = 1L; @Resource(name = "jms/wasmqtest/wasmqtest_QCF") private QueueConnectionFactory connectionFactory; @Resource(name = "jms/wasmqtest/Request_Q") private Queue requestQueue; private QueueConnection connection; private String text = ""; public void sendMessage() { System.out.println("Connection in sendMessage: \n" + connection); TextMessage msg; try { QueueSession queueSession = connection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE); QueueSender sender = queueSession.createSender(requestQueue); msg = queueSession.createTextMessage(text); sender.send(msg); queueSession.close(); sender.close(); } catch (JMSException e) { // TODO Auto-generated catch block e.printStackTrace(); } text = ""; } @PostConstruct public void openConenction() { System.out.println("Open Connection"); try { connection = connectionFactory.createQueueConnection(); connection.start(); System.out.println("Connection in OpenConnectioN: \n" + connection); } catch (JMSException e) { e.printStackTrace(); } } @PreDestroy public void closeConnection() { try { System.out.println("Closing Connection"); connection.close(); } catch (JMSException e) { e.printStackTrace(); } } public void setText(String text) { this.text = text; } public String getText() { return text; } } In PostConstruct method the connection is initialized: [21.10.13 07:36:05:574 CEST] 00000025 SystemOut O Connection in OpenConnectioN: com.ibm.ejs.jms.JMSQueueConnectionHandle@36c9b1a managed connection = com.ibm.ejs.jms.JMSManagedQueueConnection@3657e8b physical connection = com.ibm.mq.jms.MQXAQueueConnection@36618b6 closed = false invalid = false restricted methods enabled = false open session handles = [] temporary queues = [] But in sendMessage() method it isnt and I get a ConnectionClosed Problem: [21.10.13 07:36:12:493 CEST] 00000025 SystemOut O Connection in sendMessage: com.ibm.ejs.jms.JMSQueueConnectionHandle@36c9b1a managed connection = null physical connection = null closed = true invalid = false restricted methods enabled = false open session handles = [] temporary queues = [] 21.10.13 07:36:12:461 CEST] 00000025 SystemErr R 15 [WebContainer : 3] INFO org.apache.bval.jsr303.ConfigurationImpl - ignoreXmlConfiguration == true [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R javax.jms.IllegalStateException: Connection closed [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at com.ibm.ejs.jms.JMSConnectionHandle.checkOpen(JMSConnectionHandle.java:821) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at com.ibm.ejs.jms.JMSQueueConnectionHandle.createQueueSession(JMSQueueConnectionHandle.java:206) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at de.volkswagen.wasmqtest.queue.MQRequest.sendMessage(MQRequest.java:51) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at java.lang.reflect.Method.invoke(Method.java:611) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.el.parser.AstValue.invoke(AstValue.java:262) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.myfaces.view.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:83) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component._MethodExpressionToMethodBinding.invoke(_MethodExpressionToMethodBinding.java:88) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.myfaces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:100) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UICommand.broadcast(UICommand.java:120) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UIViewRoot._broadcastAll(UIViewRoot.java:973) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:275) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UIViewRoot._process(UIViewRoot.java:1285) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:711) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.myfaces.lifecycle.InvokeApplicationExecutor.execute(InvokeApplicationExecutor.java:34) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at org.apache.myfaces.lifecycle.LifecycleImpl.executePhase(LifecycleImpl.java:171) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at javax.faces.webapp.FacesServlet.service(FacesServlet.java:189) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1147) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:722) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:449) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:178) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:1020) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3703) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:304) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:953) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1655) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:195) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:452) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:511) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:305) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:83) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905) [21.10.13 07:36:12:605 CEST] 00000025 SystemErr R at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1650) Do you have an idea why the connection is closed?

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  • Design pattern for window management in a Java Swing app

    - by Lord Torgamus
    I've just started creating my very first little Java Swing app. When the program opens, it brings up a single, simple window with a label and a couple buttons. Clicking one of those buttons is supposed to wipe out the welcome screen and replace it with a totally different panel. I'm not sure what the best way to create that functionality is. One method would be to pass my JFrame as an argument into... just about every other component, but that feels hacky to me. Or, there's making each panel double as an action listener, but that doesn't seem right, either. Is there a design pattern I should be applying here? "Replace the contents of the main — and only — window" must be a reasonably common operation. A name for the pattern would be enough; I can use Google on my own from there. (I wouldn't say no to a longer explanation, though.)

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  • Why do you hate Java? Is it the language or the framework? [closed]

    - by zneak
    According to you all, Java is the third most-hated language here. The two other most hated languages are PHP and VBScript. (It's quite funny how they stand together on the podium.) I'd like to make it known that the question mostly addresses people who don't like Java. I assume here a number of subjective opinions as facts because they're usually considered true among people who don't like Java, and I don't want to be convinced otherwise here. If you're a Java enthusiast, you might find this question frustrating. It's never been made clear if people hate Java itself, or if they hate it because of the framework, or if it's a mixture of the two. On a side you have the language, where you have: the "everything should be an object" philosophy, even in instances where it should obviously be something else (event handlers I'm pointing you); checked exceptions; the idea that all logic should be presented as methods and properties is a big no-no; the fact that "closures" created by anonymous types only include final variables and arguments, but will allow write access to any member of the parent class; a few more. On the other side, you have the JDK, with... its load of inconsistencies and overengineering; monolithic class hierarchies; meaningless base exceptions like IOException (though other frameworks have similar exception hierarchies); sluggish responsiveness even with Swing; a few more. My question is, do you think that, if either one (Java or the JDK) was taken alone, and the other was dropped in favor of something else, the new combination would be better? For instance, if you could use the C# syntax with the JDK (adapting get*/set* methods into properties, and interfaces with only one method into delegates), or the Java syntax with the .NET Framework (doing the inverse transformations), would things get better in your opinion?

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  • how to think like a computer scientist java edition exercise 7.2 [on hold]

    - by James Canfield
    I cannot figure out how to write this program, can someone please help me?! The purpose of this method is to practice manipulating St rings. Create a new program called Name.java. This program will take a name string consisting of EITHER a first name followed by a last name (nonstandar d format) or a last name followed by a comma then a first name (standard format). Ie . “Joe Smith” vs. “Smith, Joe”. This program will convert the string to standard format if it is not already in standard format. Write a method called hasComma that takes a name as an argument and that returns a boolean indicating whether it contains a comma. If i t does, you can assume that it is in last name first format. You can use the indexOf String m ethod to help you. Write a method called convertName that takes a name as an argument. It should check whether it contains a comma by calling your hasComma method. If it does, it should just return the string. If not, then it should assume th at the name is in first name first format, and it should return a new string that contains the name converted to last name comma first format. Uses charAt, length, substring, and indexOf methods. In your main program, loop, asking the user for a n ame string. If the string is not blank, call convertName and print the results. The loop terminat es when the string is blank. HINTS/SUGGESTIONS: Use the charAt, length, substring, and indexOf Str ing methods. Use scanner for your input. To get the full line, complete with spaces, use reader.nextLine()

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  • Is there a canonical book for learning Java as an experienced developer?

    - by Steven Elliott Jr
    I have been a .NET developer now for about the past 5/6 years give or take. I have never done any professional Java development and the last time I really touched it was probably back in college. I have been toying with the Scala language a little bit but nothing serious. Recently, I've been offered an opportunity to do some pretty cool work, but using Java instead of .NET. I think I can get by alright with my current skill set, meaning I already know how to program well and am familiar with languages such as C# and C++, etc. So, the syntax and all that language stuff are really not a problem. What I need is a really good reference book and a book about how to think in Java. Each language/Framework/Stack tries to address things a certain way and I'm sure Java is no different. What are some great Java books that you simply can't live without? Are there any books that talk about the most important parts of Java that must be understood before all else? As a side note, I will be doing mostly Java web development. Not really 100% on what types of stuff they are using for persistence, framework, server, etc.

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  • Java keyboard input [on hold]

    - by dØd
    I'm trying to implement a input system that can detect whether a certain key was held or was only pressed briefly. So far I have this: KEY_INTERACTION_TRESHOLD = 400ms //inside a constructor shouldMeasure = true; @Override public void keyPressed(KeyEvent e) { if (shouldMeasure) { startTime = System.currentTimeMillis(); shouldMeasure = false; return; } System.out.println("Button is held down"); e.consume(); } @Override public void keyReleased(KeyEvent e) { if (System.currentTimeMillis() - startTime < KEY_INTERACTION_TRESHOLD) { System.out.println("Button was only pressed briefly"); } startTime = 0; shouldMeasure = true; e.consume(); } Now this works, but the problem is that there is this delay between when I press a key to hold and when the message 'Button is held down' gets displayed. I understand why this delay occurs (for example when you press and hold a letter there will be a similar delay between the first and the second letter printed out), but I would like to somehow avoid it. I'm using only the Java API.

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  • Implementing Circle Physics in Java

    - by Shijima
    I am working on a simple physics based game where 2 balls bounce off each other. I am following a tutorial, 2-Dimensional Elastic Collisions Without Trigonometry, for the collision reactions. I am using Vector2 from the LIBGDX library to handle vectors. I am a bit confused on how to implement step 6 in Java from the tutorial. Below is my current code, please note that the code strictly follows the tutorial and there are redundant pieces of code which I plan to refactor later. Note: refrences to this refer to ball 1, and ball refers to ball 2. /* * Step 1 * * Find the Normal, Unit Normal and Unit Tangential vectors */ Vector2 n = new Vector2(this.position[0] - ball.position[0], this.position[1] - ball.position[1]); Vector2 un = n.normalize(); Vector2 ut = new Vector2(-un.y, un.x); /* * Step 2 * * Create the initial (before collision) velocity vectors */ Vector2 v1 = this.velocity; Vector2 v2 = ball.velocity; /* * Step 3 * * Resolve the velocity vectors into normal and tangential components */ float v1n = un.dot(v1); float v1t = ut.dot(v1); float v2n = un.dot(v2); float v2t = ut.dot(v2); /* * Step 4 * * Find the new tangential Velocities after collision */ float v1tPrime = v1t; float v2tPrime = v2t; /* * Step 5 * * Find the new normal velocities */ float v1nPrime = v1n * (this.mass - ball.mass) + (2 * ball.mass * v2n) / (this.mass + ball.mass); float v2nPrime = v2n * (ball.mass - this.mass) + (2 * this.mass * v1n) / (this.mass + ball.mass); /* * Step 6 * * Convert the scalar normal and tangential velocities into vectors??? */

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